Well casing protector



Patented June 30, 1936 UNITED STATES PATENT oFFlcE WELL CASING PROTECTOR William I. Bettis, Los Angeles, Calif.

Application August 2l, 1935, Serial No. 37,198

2 Claims. (Cl. 30S- 4) This invention relates to improvements in well drilling and specifically to protectors for well casings and drill pipe and which surround the latter, and which general kind of device is now wellknown in the art.

Among the objects of this invention are: to provide a protective sleeve adapted to surround the drill-pipe or stem, and made of a suitable resilient material, as rubber, and whichis held in position by its grip on said drill-pipe. The purpose of this protector is to prevent serious or injurious impact between the moving drillstem and the well casing by interposltion of said yielding protector between them, which serves to diminish the distance apart of the casing wall and the tool stringjby said protector sleeves, which sleeves form enlargements onthe moving stem and which reduce, or absorb, any impact between the casing and drill-stem by the wellknown bufferl action of interposed yielding objects. Such sleeve can move longitudinally on the stem under strong axial forces.

Other objects are: to provide ample space or volume in a part of the wall of the protector, or elsewhere, into which space portions of the elastic material may enter when the sleeve is distorted by impact; and'to provide an especially tight lit between each end of the rubber sleeve and the drill-stem it surrounds, so that a liquid-tight seal is provided between them. Also to provide such protector that will be durable, reliable, and which can be produced at a low cost.

Other objects will appear as this specification proceeds. v

This invention constitutes an improvement on the disclosures of Patent No. 1,573,031, of February 16,. 1926, granted to myself and L. H. Perry, and is a departure from the disclosures of my Patent No. 1,863,740, of June 2l, 1932, as will appear from the drawing and the succeeding description.

As is well-known in the well drilling art and explained in the prior patents referred to, the casing and the drill-stem therein, cannot be maintained concentric, and as drilling proceeds such as rubber, are easily distorted, but diilicult to compress into smaller volume. A slight pressure on a block of rubber, between two opposing planar members, will flatten the block considerably, but it will extend, correspondingly, on all of the free sides, its volume remaining substantially constant. Or, if a rubber block be placed in a confining box having an inwardly movable cover, it is not possible to squeeze the cover down into the box and so compress the rubber except very slightly, even under great pressure, because there is no direction in which the rrubber can correspondingly extend itself as the force is applied to squeeze it thinner and it strongly resists substantial change in volume. This characteristic has been appropriately provided for in this new protector, as will appear.

With the foregoing and other objects in view, the invention consists in the novel and useful formation, construction, interrelation and combi'- nation of parts, members and features, as well as'mode and methods of use thereof, and steps and performances taken and had, all as hereinafter described, shown in the drawing and finally pointed out in claims.

In the drawing:

Fig. 1 is an elevation of the protector or buffer sleeve, partly in section and partly broken away to show thel inner walls thereof.

Fig. 2 is a diametral section on line 2-2 of Fig. 1.

Fig. 3v is the same as Fig. 1 with the protector stretched and in place on a fragmentary portion of a drill stem just above a joint in the stem.

The outer surface of the protector or buffer sleeve, indicated at A, is a plain cylinder with bevelled ends, which latter are indicated at Ill. 'Ihe bore of the sleeve has two different diameters. For a short axial distance .at each end, the diameter indicated at I2 is smaller than the bore along the middle section, between the inner bevels I3 as shown in Fig. l. In the inner wall of the sleeve A between the bevels I3 and including that portion having the greater diameter, a plurality of pockets or recesses I4 are formed as shown. These recesses provide spaces for the material of the sleeve, e. g., rubber, to expand into when the sleeve is distorted by impact or external pressure.

deep, `yet permit easy withdrawal of the core or inner mould. ,If these pockets were made with walls perpendicular to each other or having an angular cross-section, it would be impossible to withdraw the inner core on which the sleeve is formed by application of an axial force thereto, unless the depressions are very shallow, because no radial force would be set up to stretch the sleeve under such conditions. But, by using the sloping wall form of cavity, the protruding portions on the core tend to wedge the inner wall of the sleeve outward when an axial force is applied to the core, as is obvious, and thus set up a radial force to stretch the sleeve and permit easy removal of the core, leaving depressions in the wall of the material which are comparatively deep over the greater part of their areas, but which depth slopes to zero around the edges of the depressions. Heavy stresses encountered in drilling tend to bodily displace the protectors. Also, continual and repeated blows against a buffer sleeve wil! ultimately beat it into a distended form which takes a permanent set and tends to loosen its grip on the drill stem. This latter effect may be practically counterbalanced in two ways, one being to provide a sufiiciently thick wall of the elastic material, which prolongs the time of use or increases the number of blows through which a buffer sleeve will last arid retain its grip; the other way is to provide an ample amount of space in recesses positioned so that the material can ow into and out of the recesses under' impact, as before explained. Also, the contact between protector and drill stem must be maintained liquid-tight because entry of liquid between the sleeve and the stem will loosen the grip of the sleeve on the stem. If the seal between the drill stem and the sleeve is made by stretching the sleeve very considerably in order to pass it over the stem and the couplings, the resistance to stretch would be very great if the en- `tire length of the sleeve had to be stretched so much to pass over the stem. But, by making the bore of the two short end sections only small enough to require considerable stretch, while the bore of the major portion of the sleeve length is larger thanat the ends, the dilculty of stretching the sleeve sufficiently to pass over the drill stem and joints is greatly reduced, although it is held against the stem very tightly at the ends. Also, this smaller internal diameter at the ends provides a greater quantity of. material per unit length in the wall at these short end portions. So, by making the radial thickness at the sleeve ends great enough, and the bore small, these end portions can resist a considerable amount of l pounding without stretching appreciably, so that they neither lose their grip on the stem nor admit liquid between these two members. The deeper the protector is sunk in the Well, the greater becomes the surrounding liquid pressure to hold the sleeve tightly against the stem, provided none of the liquid under the same pressure can enter between drill stem and the sleeve. If the two pressures should be thus equalized, the grip of the sleeve is impaired. The middle portion, where the bore is greater than at the end, has less thickness of material and, therefore, does not require so much stretch to force this part of the sleeve over the stem. Hence, by this form, the total force required to extend the sleeve sufficiently to pass over the stem and couplings is not very great, although the grip at the ends is comparatively very strong. Such a coupling, on the drill stem is shown at C, lf'lg. 3, in which B is a fragl.eiects of impact are compensated for by making changes in the sizes, proportions, configurations,

mentary part oi a drill stem or pipe, screwed into joint or coupling C, the sleeve being shown stretched over the stem adjacent the joint and in operative position.

Continued impact on the thinner mid portion cannot damage or extend the material because the recesses I4 provide for reception of the distorted or crowded or displaced parts. A blow against the outer surface merely drives some of the material into new positions for the instant, and, as there is ample space to permit the material to move into, and, resiliently, back out of the spaces Il, the wall of the sleeve is not pounded thinner except at the ends, where the the walls thicker.

The bevelled ends I0 are to prevent the sleeves from striking or catching against any part of the well or casing or other external object when the stem is moved into or out of the well, as is 2O obvious. Since the bore at the ends and that of the mid section are both of less diameter than that of the drill stem, the entire sleeve is stretched when in position over the stem, hence the two different sized bores become of equal diameter, 25

thus making the stretched inner wall a smooth continuous surface, as indicated in Fig. 3, but the tightness of grip and the quantity of material per unit length at the ends are greater than at the mid section as, and for the purposes, ex- 30 plained. The grip on the stem in the mid section is only at those portions I I extending between the perimeters of the depressions I4 as indicated.

The arched wall formation of the cavities I4 35 effectively distributes stresses imparted to the sleeves over large pipe area.

Having described my invention in connection with illustrative embodiments, forms, proportions and arrangements of parts, it -willbe un- 40 derstood that many variants thereof are possible to those skilled in the art, and my invention, in its broader aspects, is not limited to the speciiic construction herein described and shown, as

arrangements, assemblage, interaction, juxtapo, sition and mechanical relations, as well asI additions, omissions, substitutions, combinations and alterations of forms, parts, members and features, may be made without departing from the broad spirit of this invention.

Having thus disclosed my invention, I claim and desire to secure by Letters Patent:

1. A Well casing protector comprising a body of yielding material for surrounding and gripping a member of a drilling tool string; the interior of said body normally having variations vin diameter, said interior likewise being recessed, said recessed portion being a portion of major internal diameter.

2. A protector comprising a sleeve of yielding material for gripping a member of a tool string; said sleeve having end portions of extensive internal superficial area acting as seals to prevent invasion of liquid or fluid between the sleeve and thel tool string member; the interior surface of said sleeve likewise having a plurality of recesses of arcuate form tending to accommodate displacement of the sleeve material in allV direcr tions and by the arched wall conformation thereof distributing stresses imparted to said sleeve over extended inner superficial area thereof.

' WILLIAM I. BE'I'I'IS. 

